Installer resides at /Applications/Utilities/Installer.app on Macintosh computers running OS X versions prior to 10.5, and launches when a package or metapackage file is opened. In OS X Yosemite, the Installer application is located at /System/Library/CoreServices/Installer.app. The installation process itself can vary substantially, as Installer allows developers to customize the information the user is presented with. For example, it can be made to display a custom welcome message, software license and readme. Installer also handles authentication, checks that packages are valid before installing them, and allows developers to run custom scripts at several points during the installation process.[2]